I don’t think math _______.
| A．easily to be learned | B．easily to learn |
| C．easy to be learned | D．easy to learn |
Although the causes of cancer_____, we do not yet have any practical way to prevent it.
| A．are being uncovered | B．have been uncovering |
| C．are uncovering | D．have uncovered |
With just four years _______, the Brazil Olympic organizers have promised to deliver an equally inspirational ceremony.
| A．gone | B．to go | C．going | D．go |
We are so sorry for that．We'll try to determine exactly _________ went wrong that evening．
| A．where | B．what | C．which | D．how |
If you go there by ____train ,you can have quite a comfortable journey ,but make sure you get ___fast one.
| A．/; / | B．/; a | C．the; a | D．the ; / |
Visitors were _____at the _____pictures that the guide showed.
| A．amazed; amazing | B．amazed; amazed |
| C．amazing; amazing | D．amazing; amazed |